SIGNIFICANT RULES

• The court

  The game is played on a volleyball court 18 meters (59 feet) long and 9 meters (29.5 feet) wide, divided into two 9 m x 9 m halves by a one-meter (40-inch) wide net placed so that the top of the net is 2.43 meters (7 feet 11 5/8 inches) above the center of the court for men's competition, and 2.24 meters (7 feet 4 1 / 8 inches) for women's competition (these heights are varied for veterans and junior competitions).
• There is a line 3 meters from and parallel to the net in each team court which is considered the "attack line". This "3 meter" (or 10 foot) line divides the court into "back row" and "front row" areas (also back court and front court). These are in turn divided into 3 areas each: these are numbered as follows, starting from area "1", which is the position of the serving player:
• After a team gains the serve (also known as siding out), its members must rotate in a clockwise direction, with the player previously in area "2" moving to area "1" and so on, with the player from area "1" moving to area "6".
• The team courts are surrounded by an area called the free zone which is a minimum of 3 meters wide and which the players may enter and play within after the service of the ball. All lines denoting the boundaries of the team court and the attack zone are drawn or painted within the dimensions of the area and are therefore a part of the court or zone.
• If a ball comes in contact with the line, the ball is considered to be "in". An antenna is placed on each side of the net perpendicular to the sideline and is a vertical extension of the side boundary of the court. A ball passing over the net must pass completely between the antennae (or their theoretical extensions to the ceiling) without contacting them.
• The ball

  FIVB regulations state that the ball must be spherical, made of leather or synthetic leather, have a circumference of 65-67 cm, a weight of 260-280 g and an inside pressure of 0.30-0.325 kg/cm2. Other governing bodies have similar regulations.
• Scoring

  When the ball contacts the floor within the court boundaries or an error is made, the team that did not make the error is awarded a point, whether they served the ball or not.
• If the ball hits the line, the ball is counted as in. The team that won the point serves for the next point. If the team that won the point served in the previous point, the same player serves again.
• If the team that won the point did not serve the previous point, the players of the team rotate their position on the court in a clockwise manner. The game continues, with the first team to score 25 points (and be two points ahead) awarded the set. Matches are best-of-five sets and the fifth set (if necessary) is usually played to 15 points. (Scoring differs between leagues, tournaments, and levels; high schools sometimes play best-of-three to 25; in the NCAA games are played best-of- five to 25 as of the 2008 season.)
• Before 1999, points could be scored only when a team had the serve (side-out scoring) and all sets went up to only 15 points.
• The FIVB changed the rules in 1999 (with the changes being compulsory in 2000) to use the current scoring system (formerly known as rally point system), primarily to make the length of the match more predictable and to make the game more spectator- and television-friendly.
• Libero

  In 1998 the libero player was introduced internationally. The libero is a player specialized in defensive skills: the libero must wear a contrasting jersey color from his or her teammates and cannot block or attack the ball when it is entirely above net height.
• When the ball is not in play, the libero can replace any back-row player, without prior notice to the officials. This replacement does not count against the substitution limit each team is allowed per set, although the libero may be replaced only by the player whom he or she replaced.
• The libero may function as a setter only under certain restrictions. If she/he makes an overhand set, she/he must be standing behind (and not stepping on) the 3-meter line; otherwise, the ball cannot be attacked above the net in front of the 3-meter line. An underhand pass is allowed from any part of the court.
• The libero is, generally, the most skilled defensive player on the team. There is also a libero tracking sheet, where the referees or officiating team must keep track of who the libero subs in and out for. There may only be one libero per set (game), although there may be a different libero in the beginning of any new set (game).
• Furthermore, a libero is not allowed to serve, according to international rules, with the exception of the NCAA women's volleyball games, where a 2004 rule change allows the libero to serve, but only in a specific rotation.
• That is, the libero can only serve for one person, not for all of the people for whom he or she goes in. That rule change was also applied to high school and junior high play soon after.
• Recent rule changes

  Other rule changes enacted in 2000 include allowing serves in which the ball touches the net, as long as it goes over the net into the opponents' court.
• Also, the service areawas expanded to allow players to serve from anywhere behind the end line but still within the theoretical extension of the sidelines.
• Other changes were made to lighten up calls on faults for carries and double-touches, such as allowing multiple contacts by a single player ("double-hits") on a team's first contact provided that they are a part of a single play on the ball.
• In 2008, the NCAA changed the minimum number of points needed to win any of the first four sets from 30 to 25 for women's volleyball (men's volleyball remained at 30.)
• If a fifth (deciding) set is reached, the minimum required score remains at 15. In addition, the word "game" is now referred to as "set".
• Changes in rules have been studied and announced by FIVB in recent years, and they have released the updated rules in 2009.